Monday, April 9, 2018

Season 11 superfinal, games 51-60

After 60 games Stockfish leads 13-1 with 46 draws. The last 10 games have all been draws, Stockfish may be taking a break since it is almost surely going to win the match.

Houdini was a pawn up after the start of game 51. All pieces remained on the board as the engines started to shuffle on move 19. After 35 moves Houdini gave a rook for a bishop, and the position opened up. After a series of exchanges only RR vs BNN remained, Houdini with 3 extra pawns. Evals were close to 0 despite the unusual material imbalance, a white passer cost Houdini a knight, the engines then traded pieces until reaching a tablebase draw. In game 52 the engines kept the pieces on the board for the first 35 moves. Stockfish was a pawn up with a queen side passer and eval above 1. After a few exchanges the evals dropped and the engines started to shuffle. At move 112 the engines started to open the position, after clearing the queen side the game was adjudicated.

Stockfish started game 53 with an eval advantage with all pieces on the board. The engines were close to a 3-fold repetition on move 17, instead the pawns locked the queen side and the engines exchanged a few pieces and pawns. The position opened a little and the engines exchanged most pieces, Houdini gave a knight for pawns to break the white pawn line on the king side. The game reached a bishop vs pawns ending, Houdini was 3 pawns up. The result was a draw though it took 65 shuffling moves to get there. In game 54 the engines were essentially shuffling from move 19. Evals turned negative but stayed constant. The pawns stopped moving on move 49 as the shuffling continued. On move 119 The engines started to open the position with exchanges, reaching a drawn knight ending.

Game 55 started with Stockfish a pawn up and Houdini's king in the center unable to castle. Stockfish's eval was over 1 but more or less stable. The position became static, then after a series of exchanges only QNN vs QNN were left. After exchanging a pair of knights Stockfish's queen moved forward, and Houdini managed to trap it in the corner. For a while Stockfish thought it was ahead with eval approaching 2, but it soon realized there was no way to improve. After exchanging queens the evals dropped to 0, the game continued until getting a tablebase draw. In game 56 Houdini chose a different line, not forcing the black king to move but winning a rook temporarily. Stockfish countered with an attack on the white king, forcing it to move without castling. Stockfish regained the material by move 17 and evals were close to 0. The game reached a knight ending and a draw.

Stockfish had an eval advantage close to 1 in game 57. It went a pawn up on move 16, and after a series of exchanges only BN vs BN were left on move 28. The extra pawn was not enough, the game reached a tablebase draw. In game 58 evals came down to 0 faster. Material was balanced as the engines exchanged pieces. Houdini grabbed a pawn before exchanging queens, reaching a N vs B ending on move 34. Stockfish got the pawn back and the game was adjudicated a few moves later.

There were many early exchanges in game 59, with only RRB vs RRN remaining on move 22. Stockfish's eval jumped over 1 when it took over the 7th rank, and jumped again over 1.5 after trading minor pieces. It appeared that Stockfish was ahead with an advanced queen side passer, however Houdini put its rooks on the 2nd rank and could end the game with a perpetual check. Houdini chose to play on, only delaying the draw by a few moves. In game 60 evals were low throughout the game. After move 13 there were no exchanges for 20 moves. After the position opened up the white king was exposed. Stockfish attacked and started a series of exchanges that led to a drawn B vs N ending.